netdev - [PATCH 1/2] HTB scheduler, change default hysteresis mode to off.

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Date:	Tue, 03 Jun 2008 16:05:07 +0200
From:	Jesper Dangaard Brouer <jdb@...x.dk>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Martin Devera <devik@....cz>
Subject: [PATCH 1/2] HTB scheduler, change default hysteresis mode to off.


The HTB hysteresis mode reduce the CPU load, but at the
cost of scheduling accuracy.

On ADSL links (512 kbit/s upstream), this inaccuracy introduce
significant jitter, enought to disturbe VoIP.  For details see my
masters thesis (http://www.adsl-optimizer.dk/thesis/), chapter 7,
section 7.3.1, pp 69-70.

Signed-off-by: Jesper Dangaard Brouer <hawk@...x.dk>
---
 net/sched/sch_htb.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 5bc1ed4..9134f02 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -53,7 +53,7 @@
 */
 
 #define HTB_HSIZE 16		/* classid hash size */
-#define HTB_HYSTERESIS 1	/* whether to use mode hysteresis for speedup */
+#define HTB_HYSTERESIS 0	/* whether to use mode hysteresis for speedup */
 #define HTB_VER 0x30011		/* major must be matched with number suplied by TC as version */
 
 #if HTB_VER >> 16 != TC_HTB_PROTOVER
-- 
1.5.4.2


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